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Australia has large reserves of limonite and clay-based laterites that are currently underutilized. This review summarizes the latest nickel laterite upgrading studies reported in the literature which use physical beneficiation – only studies reported after the most recent review in 2015 included – as well as high-temperature methods involving oxidation/reduction roasting (with and without additives), sulphidation, and other high-temperature methods. The focus of this review is on upgrading limonite ores, but studies using other types of laterites are also discussed for comparative purposes. Oxidative roasting has proven to be ineffective but producing a magnetic phase by reduction roasting then magnetically separating it from gangue minerals has produced nickel grades and recoveries of up to 14% and 99% respectively with limonite ores. The choice of reductant has negligible effect although hydrogen reduction is predicted to occur at slightly lower temperatures and recoveries are slightly lower compared with carbon-based reductants. The addition of sulfurous compounds improves agglomeration of ferronickel particles, increases the nickel grade and recovery. The highest recovery of 97.91% (grade 13.62%) was reported when sulfur was used as an additive during the roasting of a limonite ore with coal and limestone at 1400°C for 6 h. The results show reduction roasting followed by magnetic separation is effective for upgrading nickel ores, but challenges with this technology are the potentially high reagent usage and temperatures required. The economic feasibility for processing limonite ores via this route is not clear and should be investigated further. [ABSTRACT FROM AUTHOR]

In this study, we investigated a nickel laterite ore with Ni content of 1.56 wt% and a red mud with Fe content of 20.98 wt%, the main Ni-bearing mineral in the nickel laterite ore was nickel-lizardite, and the main Fe-bearing mineral in the red mud was hematite. A novel process of roasting and magnetic separation was purposed to extract nickel and iron from the nickel laterite ore and red mud. The nickel laterite ore, red mud, calcium chloride, and coke were mixed and put in a roaster for roasting, and the ferronickel concentrate was obtained from the roasted ore by magnetic separation. The results showed that a ferronickel concentrate with Ni content of 7.97 wt%, Fe content of 73.09 wt%, iron recovery of 76.87%, and nickel recovery of 90.28% was obtained under the optimal conditions: a mass ratio of m (nickel laterite ore): m (red mud) : m (coke) : m (calcium chloride) : of 0.6:0.4:0.2:0.1, a roasting temperature of 1373 K, a roasting time of 90 min, a grinding fineness of − 0.045 mm occupying 90%, and a magnetic field strength of 0.20 T. The main minerals in the ferronickel product were metallic Fe and FeNi. [ABSTRACT FROM AUTHOR]

The magnesium slag (magnesium nitrate hydrate Mg(NO3)2·6H2O) produced in the nitric acid leaching process of laterite nickel ore can be effectively recycled by thermal decomposition. To this end, this study placed great emphasis on disclosing the thermal decomposition mechanism of Mg(NO3)2·6H2O. Firstly, thermal decomposition paths of Mg(NO3)2·6H2O were revealed through Thermogravimetry-Mass Spectrometry, Differential Scanning Calorimetry and powder X-ray diffraction. It was found that the thermal decomposition of Mg(NO3)2·6H2O was a multistep endothermic reaction involving two dehydration stages and one denitration stage. The two dehydration stages were characterized by the evolution of H2O, with the formation of magnesium nitrate dihydrate and anhydrous magnesium nitrate. The denitration stage was characterized by the simultaneous evolution of O2 and NO2, with the formation of MgO. The conventional kinetic analysis was not suitable for describing such complex multistep reaction behaviour. Thus, the kinetic rate data (dα/dt-T) for the overall reaction were separated into those for three contributing stages by mathematical peak deconvolution. Then, the complete kinetic interpretations of the separated reaction stages for Mg(NO3)2·6H2O pyrolysis were achieved by the Friedman method and the master plots method. Finally, the original experimental α-T curves were successfully simulated using the resulting kinetic triplets. [ABSTRACT FROM AUTHOR]

The effects of configuration of the stirred tank and energy input on the flotation performance of nickel ores were systematically investigated in this paper. Flotation tests revealed that the stirred tanks with two impellers had an advantage over those with one impeller in intensifying agitation pretreatment, and the higher agitation speed led to a better flotation performance of nickel ores. It was also found that with baffles in the stirred tanks, the flotation grade was higher than that without baffles. Besides, the energy supplied to the system significantly influenced the flotation recovery, indicating that if the energy consumption of the agitation pretreatment is ideal, the improvement of the flotation efficiency can be achieved. Also, data from full-scale operations backed up these results. [ABSTRACT FROM AUTHOR]

Basicity is an essential parameter in the pyrometallurgy of nickel laterite processing to determine the low melting point temperatures of phases. However, its effect on selective reduction of nickel laterite is less studied. In this study, we investigated the effect of ternary basicity (CaO/(Al2O3+ SiO2)) in selective reduction process. Nickel laterite, sodium sulphate, and bituminous coal were mixed and pelletised into 10–15 mm diameter. The reduction process is carried out at a temperature of 1150°C for 60 minutes in a muffle furnace continued with the magnetic separation process. The ternary basicity values were modified with CaO addition varied from 0.1 to 1.0. Modifying basicity with CaO addition could destroy the silicate and magnesium oxide complex structure, thus releasing iron and nickel to form the metallic phase of ferronickel, which could increase the nickel grade in ferronickel. Nevertheless, excessive addition of CaO resulted in the formation of calcium silicate structures with high melting point temperatures, such as akermanite and merwinite, which could suppress the troilite and inhibit the agglomeration of ferronickel particles. The optimal ternary basicity is 0.1 (which was modified by CaO addition). It resulted in 6.08% and 88.83% of nickel grade and recovery, respectively. [ABSTRACT FROM AUTHOR]

Polymetallic nodules and nickel laterite ores are composed of various valuable metals and have similar nickel concentration, which makes them ideal alternatives for industries seeking to meet the increasing demand for nickel resources. The extraction process of polymetallic nodules can utilize the well-established nickel laterite treatment process without the need for developing new processes and thus, save capital costs. Herein, to efficiently extract nickel from these resources, high-temperature carbothermic reduction and sulfurization were investigated by optimizing the slag and matte systems. FactSage, a thermodynamic software was used to predict the slag system's liquidus temperature and the formation of nickel matte. It was found that nickel matte formation was not dependent on CaSO4 addition whereas the nickel concentration in matte decreased with an increasing amount of the sulfiding agent FeS. Furthermore, the addition of a reductant significantly affected the concentration of nickel in the matte. A nickel concentration of ≥30 wt% and iron concentration of ≤40 wt% in matte were achieved by adding 0.5 wt% and 3 wt% carbon to nickel laterite ores and polymetallic nodules, respectively. Furthermore, replacing the sulfiding agent FeS with CaSO4 during the smelting of polymetallic nodules decreased the iron concentration in matte ≤15 wt% and increased the nickel concentration ≥50 wt%. Thus, this study confirmed the possibility of matte formation with high nickel concentration and low iron content by utilizing alternative nickel resources at 1350–1450°C. [ABSTRACT FROM AUTHOR]

A two-step closed circuit, operated at 90–95ºC, was found suitable for practical iron removal from real sulfuric acid leach liquors, resulting in low losses of nickel and cobalt to the solid phase. In the first step, NH4OH was used as a reagent to treat iron-rich liquors (1.8 g.L−1 < [Fe]total <8.7 g.L−1) with an initial pH of 1.6 ± 0.1, and nickel and cobalt concentrations of 1.59 ± 0.05 g.L−1 and 108 ± 6 mg.L−1, respectively. Metal losses are greatly affected by the liquor's pH, which increased when liquors with respective higher initial [Ni]/[Fe] and [Co]/[Fe] concentration ratios were treated. Losses were mostly associated with adsorption reactions on the surface of the precipitate, identified mainly as jarosite and goethite phases. Iron removal higher than 99% was obtained at pH 2.5–3.3, with metal losses of up to 1.8%. In the second step, milk of lime (1.5 CaO g/100 mL) was used as a reagent. A final solution containing only 2.1 mg.L−1 of iron, with nickel and cobalt losses below 1.6%, was achieved at pH 3.7–3.8; the precipitate was identified as bassanite. The precipitates presented rapid sedimentation and good filterability, which were observed visually. Filtration operation should be carried out at temperatures above 80°C. A brief review of the literature is also presented. [ABSTRACT FROM AUTHOR]

The microwave drying of a Philippine nickel laterite ore was proposed as an alternative drying method to reduce the air pollution before further pyrometallurgical processing. The effect of thickness of ore bed and microwave power on the specific energy consumption and effective diffusivity were assessed. The results show that the specific energy consumption decreases with increasing the bed thickness and that the specific energy consumption exhibits a minimum at 1200 W. Besides, the increase of nickel laterite thickness and microwave power promotes the effective diffusivity. Compared with the removal of free water, crystalline water removal is proved to be much more energy-intensive. Furthermore, the specific energy consumption in microwave drying of laboratory scale is substantially higher than commercial rotary kiln drying. [ABSTRACT FROM AUTHOR]

The inhalation of dust containing certain nickel compounds has been associated with an increased risk of lung and nasal cancers in occupational studies of workers who process or refine sulfidic nickel ores and are exposed to relatively high levels of mixtures of water-soluble, sulfidic, oxidic, and/or metallic forms of nickel. We conducted a systematic review of the potential carcinogenicity of metallic nickel, focusing on cancers of the respiratory tract. We evaluated the quality and risk of bias (RoB) of the relevant epidemiology, experimental animal, and in vitro mechanistic studies using the National Toxicology Program's Office of Health Assessment and Translation (OHAT) RoB Rating Tool. We then used a systematic review protocol based on the OHAT approach to critically assess whether metallic nickel should be considered a human respiratory carcinogen. Our evaluation of the epidemiology studies indicates that there is no substantive evidence of increased respiratory cancer risk in workers exposed predominantly to metallic nickel. Animal evidence indicates that metallic nickel does not increase the incidence of respiratory tumors in rodents exposed by inhalation. The in vitro studies are limited in value, as they bypass normal clearance mechanisms. Nevertheless, the mechanistic evidence indicates that metallic nickel is not mutagenic but can induce DNA strand breaks under certain conditions. Based on a standard framework for assessing causality, we conclude that the evidence does not support a causal relationship between metallic nickel exposure and respiratory cancer in humans. [ABSTRACT FROM AUTHOR]

Acted by waves, swing and vibration of the vessel, the granular bulk cargo which contains certain moisture content may liquefy and behave like a fluid in cargo hold. When the liquefaction of the cargo occurs, it can cause the vessel to list or even capsize. In this study, based on a computational fluid dynamics (CFD) solver and non-Newtonian constitutive equations, a numerical model was developed to study the sloshing of nickel ore slurry in a cargo hold. The volume of fluid method was used to capture the movement of the fluid interface. To validate the proposed model, the numerical results were verified by comparison with available experimental data. To fully understand the sloshing behaviour of the nickel ore slurry in the hold, the dimensional analysis was accomplished by using the Buckingham π theorem. Designating the mean sloshing-induced moment amplitude as an indicator, the deduced eight non-dimensional parameters governing the sloshing of the nickel ore slurry in the cargo hold were investigated by two different scaled models. Furthermore, the parametric studies of the excitation frequency, excitation amplitude and depth to width ratio on the sloshing-induced moment are discussed extensively and some conclusions are obtained. [ABSTRACT FROM PUBLISHER]

In Part II, the correlation between Fe–Ni grain growth and characteristic fusion temperatures of the Na2SO4–laterite mixtures, and phase transformations of the reduced pellets were investigated. For the mechanism of sodium sulphate, Na+is able to liberate the hosted nickel and iron within lizardite, while SO42–is the sulphur source for the formation of Fe–FeS eutectic compound which can decrease the characteristic fusion temperatures to promote the growth of ferronickel grains. The mean particle size of ferronickel increased from 7.4 μm to 48.6 μm with the addition of 20 wt% Na2SO4. [ABSTRACT FROM PUBLISHER]

The selective reduction of nickel and adequate growth of ferronickel grains are imperative for efficient preparation of ferronickel from nickeliferous laterite ore via the process of direct reduction followed by magnetic separation. In Part I, reduction/sulfidation behaviors of a saprolitic laterite ore in the presence of sodium sulfate were investigated, with an emphasis on thermodynamic analysis, selective reduction/sulfidation ratios and kinetics. To separate the interactions between Ni and Fe, chemical titration analysis was adopted to determine the contents of various Ni and Fe species in the roasted pellets, and a modified equation to assay metallic iron content was proposed. [ABSTRACT FROM AUTHOR]

The mineral phases in more than 50 Ni laterite ores were determined before and after the ores were acid-leached in columns for more than 120 days. The selected ore samples have wide variations in initial chemical and mineralogical compositions and other properties, and their behaviour during treatment, including the proportions of Ni and Co extracted, exhibit similar extreme variations. Ores contain up to 13 quantifiable phases, including iron, manganese and chromium oxides, carbonates, kaolinite, serpentine, talc, chlorite, smectite, albite, hornblende and quartz. The highest Ni and Co concentrations were in the Mn-oxide phases that comprised <10 wt% in all test ores. Ores with high Ni grades (1.4–2.1 wt%) contained mainly smectite or chlorite, with low abundances of goethite and a variety of poorly crystalline phases. High Ni extractions (88–96%) during leaching were achieved mainly from low-goethite ores, but goethite abundance was not the only factor that influenced Ni extraction. Examination of the elements substituted in goethite indicated that greater Ni extraction was achieved from ores in which the Fe was partly replaced by Ni or Co. The cobalt grade in ores was related to the abundance of Mn-oxide phases, but the percentage of Co extracted during leaching did not correlate strongly with the abundance of any particular mineral phases. Cobalt extractions of >80% were achieved for only 12% of the ores tested in this study. While mineralogy ultimately determines the acid consumption of an ore, the mineral matrix in this suite of Ni laterites was sufficiently complex to prevent a simple predictive estimate. [ABSTRACT FROM AUTHOR]

The distribution of Ni in four lateritic Ni-goethites that were rapidly dehydroxylated to form hematite by shock heating at 340/400°C and 800°C for 30 min was investigated using synchrotron X-ray diffraction (SXRD), TEM spectroscopy (EELS and EFTEM) and synchrotron X-ray absorption spectroscopy (XAS). The Ni K-edge EXAFS results for non-heated samples showed three distinct Ni–Fe shells, including two edge-sharing (R Ni–Fe ∼ 3.01 and R Ni–Fe ∼ 3.22 Å) and a double corner-sharing (R Ni–Fe ∼ 3.52 Å) complex for most of the samples. These interatomic distances are indicative of Ni substituting for Fe in goethite, which has resulted in an expansion in the goethite structure along the a-axis direction and a contraction along the b-axis direction. Ravensthorpe Ni goethite was considerably different from the other goethites, with two Ni–O interatomic lengths (R Ni–O ∼ 2.04 and 2.46 Å), an edge-sharing (R Ni–Fe ∼3.04 Å) and a corner-sharing (R Ni–Fe ∼ 3.56 Å) complex. The R Ni–O ∼ 2.46 Å bond length is not indicative of Ni substituting for Fe in goethite, nor is it associated with single or multiple scattering events in NiO, Ni(OH)2 or Ni substituting for Fe in Fe oxides. The corresponding Ni K-edge EXAFS results for 340/400°C and 800°C heated samples (i.e. hematite) were very similar. Four distinct metal neighbours correspond to Fe/Ni in face-sharing (R Ni–Fe ∼ 2.87–2.91 Å) and three different corner-sharing complexes (R Ni–Fe ∼ 3.37– 3.41 Å, R Ni–Fe ∼ 3.62– 3.64 Å and R Ni–Fe ∼ 3.92– 4.09 Å) represent Ni substituting for Fe in hematite. The fourth shell is indicative of an inner sphere surface complex. EFTEM maps for Ni in goethite are consistent with the formation of a surface complex as they provide evidence for clustering of Ni on the surface of neoformed hematite crystals. There was no evidence from EXAFS or SXRD supporting the formation of discrete Ni phases (e.g. NiO) as a result of shock heating. Therefore, for Ni-goethites subjected to shock heating at 800°C (i.e. high-temperature dehydroxylation to hematite), most of the Ni is retained in the structures of the neoformed hematites, whereas some of the Ni migrates to the surface of the neoformed hematite where it forms a surface complex. During acid dissolution (e.g. heap leaching) of oxide-type lateritic Ni ores, Ni on the hematite surface is more accessible to acid solutions; therefore, these results may provide a basis for more efficient extraction methods for Ni in oxide-type lateritic Ni ores, as well as providing information on the possible redistribution of Ni in heated goethite-rich soils. [ABSTRACT FROM AUTHOR]

Data are presented on the solvent extraction of nickel and cobalt from sulfate solutions imitating the composition of partially neutralized liquors from the leaching of oxidized nickel ores using mixtures of 0.4 M CYANEX 301 (HR) with 0.4–0.5 M C7–C9 fraction of a trialkyl amine (R′3N) as the extractant. Nickel and cobalt are efficiently extracted in the pH range 6.2–6.5 and separated from Mn, Mg, and Ca in the extraction step. The separation factors for Co and Ni are high (102–103). Due to the formation of the stable adduct [R′3NH]+[R]− between the extractant components, nickel and cobalt can be stoichiometrically stripped with H2SO4 (1.0–2.0 M), allowing the production of concentrated solutions (> 100 g/L of total Co and Ni). The nickel strip liquors contain only a small amount of free acid (pH 1.5–2.0) after purification from cobalt, so they can be further processed using traditional technologies. A proposed flowsheet for nickel and cobalt recovery from such leach liquors has the advantages of ease of production of concentrated nickel and cobalt strip liquors in sulfate media and the stability of the extractant and strip liquor to oxidation by air or oxygen compared to other variants of CYANEX 301 applications. [ABSTRACT FROM AUTHOR]

In this review, the physical and chemical properties of the pyrrhotite group minerals are discussed, particularly their mineralogical behavior during mineral processing and phase transitions. Pyrrhotites are often associated with nickel ores and gold deposits. Consideration of the leaching processes of pyrrhotites focuses on the recovery of Ni and Au. The mechanisms of acid leaching are presented from physical, chemical, electrochemical, and crystallographic viewpoints. Other pyrrhotite processing techniques, including oxidation and flotation, are also included in this article. [ABSTRACT FROM AUTHOR]

Potential use of dissolved gas bubbles in mineral flotation processes was investigated by conducting tests on the copper–nickel ore of Inco Ltd. in Sudbury, Ontario, Canada. Such bubbles were generated by pressurizing the ore pulp in an air or argon atmosphere at a 276 kPa gauge (40 psig) for a period of about 1 min and then releasing the pressure by discharging the pressurized pulp into a column where flotation took place. Based on the conclusions of an earlier work, dissolved gas bubbles were employed together with conventional bubbles, the latter produced by a gas sparger located inside the flotation column. The presence of dissolved gas bubbles in the flotation pulp was found to have a significant impact, particularly when argon was used as the flotation gas, resulting in substantially higher grades and recoveries in the concentrate. At the same time, mass recoveries by size showed a 20% increase across all sizes when air was used as the flotation gas and a 40–100% increase in the case of argon. [ABSTRACT FROM AUTHOR]

Samples from the saprolite and extensive smectite zone (up to 25&ThickSpace;m thick) of the Murrin Murrin lateritic nickel deposit, developed from serpentinised peridotites, were studied using optical microscopy, XRD, SEM and TEM-EDX. In the saprolite zone, the initial mesh-texture of the parent rock is still well preserved. The mineralogy is dominated by serpentine, smectite and maghemite. Two kinds of smectites occur in this zone: saponites and smectites with chemistries intermediate between two dioctahedral end-members (Fe nontronite, Fe montmorillonite) and a trioctahedral one (Mg + Ni saponite). In the smectite zone, serpentine and saponite completely disappear, however some relicts of the initial mesh-texture exist. Smectite and maghemite are the dominant minerals and goethite appears at the top of this zone. Smectites from the smectite zone have a complex chemistry which appears intermediate between four dioctahedral end-members (Fe Nontronite, Fe montmorillonite, Al beidellite, Al montmorillonite) and a trioctahedral one (Mg + Ni saponite). Smectites in fissures exhibit a greater variability in Al vs Fe + Cr content than smectites from plasma; this suggests a supply of Al by the percolating fluids. Nickel, essentially concentrated in the smectite zone (1.3 wt%), is located in the octahedral sheets of the plasma and fissure-smectites with Ni content up to 0.30 per half unit-cell. The oxygen and deuterium isotopic compositions of the smectites show that they crystallised at low temperature in contact with meteoric fluids. The δ 18 O values of Murrin Murrin smectites are negatively correlated with their Fe + Cr content. [ABSTRACT FROM AUTHOR]

A study describing the effect of microwave radiation, at a frequency of 2,450 MHz, on the processes of communition and flotation of a complex sulphide nickel-copper ore is presented. Ore communition has been investigated under standard radiation-free conditions and after ore treatment in a radiated environment as a function o fore size, exposure time to radiation, and microwave power The findings show that communition is tremendously improved by microwave radiation with values of the relative work index as low as 23% at a microwave power of 1.406 kW and after 10 s of exposure time. Communition is affected by exposure time and microwave power in a nontrivial manner. In terms of ore floatability, the experimental tests have been carried out on a sample of 75 µm in size under different exposure times. The results show that both ore concentrate recoveries and grades of nickel and copper are significantly enhanced after microwave treatment of the ore with relative increases in recovered concentrate, grade of nickel, and grade of copper of 26 wt%, 15 wt%, and 27%, respectively, at a microwave power of 1,330 kW and after 30 s of exposure time. [ABSTRACT FROM AUTHOR]

The possibility of decontaminating arable soil, forest soil, and gley soil, artificially contaminated by solutions of cesium-137, strontium-85, and europium-152, by contact in common suspension with magnetic residues of leached nickel ores (SOR) from the former Sered hydrometallurgical plant and its magnetic separation was demonstrated. More than 60–98% of cesium and strontium took part in the exchange between the soil and the magnetic sorbent and could be efficiently removed at sorbent mass to soil mass ratio as large as 5. Freundlich sorption isotherms were used for the evaluation of the driving forces of the transfer process. Actual soil remediation depends on the possibility of recycling used SOR: the speciation of sorbate indicates that the retention of strontium takes place in an exchangeable form but that of cesium and europium manifests through a more strong binding to the oxide component of SOR. [ABSTRACT FROM AUTHOR]

The article focuses on a sorting system that could potentially increase the economic viability of low-grade nickel ore extraction developed by researchers at BC Research Ltd., the University of British Columbia and Vale INCO Ltd. The high-frequency electromagnetic sorting system (HFEMS) comprises of two coils, a sensor and reference. MineSense Technologies chief executive officer (CEO) Doctor Andrew Bamber states that sorting systems offer lower capital and operating costs.